Vehicle batteries provide power for a vehicle's starting, lighting, and ignition functions. In general, an automotive battery outputs a few hundred amperes of current for a few seconds of the starting period. The battery is then recharged by the charging system of the vehicle which generally consists of an alternator, rectifier, regulator, and voltage and current controllers. Alternators are used in conventional motor vehicles to convert mechanical energy produced by an internal combustion engine to electrical energy. The alternator is typically coupled to the engine by a rotating shaft to generate alternating current (AC). This current is then converted to direct current (DC), which in turn is used to power electrical circuits in the vehicle during normal driving conditions and to charge a vehicle battery.
During operation of the electrical circuits in the vehicle and charging of the battery, the charge or current provided by the alternator is usually regulated. This regulation may affect the charging efficiency of the vehicle battery as well as other vehicle maintenance requirements. Conventional regulating devices have been developed to maintain the DC alternator output voltage, commonly referred to as a voltage setpoint, within a nominal operating range. Some of these voltage regulating devices tend to be inefficient in fuel consumption when operated in conjunction with batteries of a vehicle.
Regulation strategies implemented in some conventional regulating devices have generally not been tunable or adaptable to changing load demands of the vehicle. During operation of these regulating devices, an appreciable amount of mechanical energy is typically converted to excess electrical energy, and some energy is lost that may have been used to drive or power other vehicle systems or components. The expended mechanical energy usually takes the form of engine torque, which may result in a greater expenditure of fuel to supply higher electrical loads on the vehicle. In addition, mechanical energy may be lost in the form of heat from charging the vehicle battery at relatively higher voltage levels. Increased heat losses tend to decrease efficiency and increase fuel consumption. Damage to the battery may also occur under such conditions due to battery gassing.
One approach to improving the charging efficiency of the vehicle battery has been to use regulated voltage control (RVC). RVC monitors voltage and current draw from the vehicle battery and controls the voltage output of the alternator based on such voltage and current draws. The alternator output may be regulated so as to minimize vehicle fuel consumption. For example, by taking into account a battery state of charge and the electrical energy drawn by the vehicle at a given time, an alternator setpoint voltage may be optimized so as to more closely track the electrical load requirements of the vehicle and minimize the amount of excess electrical energy generated. By optimizing the setpoint, based at least in part on the amount of stored electrical energy and estimated vehicle load, mechanical energy otherwise used to produce excess electrical energy is typically conserved and used for other purposes to generally provide a fuel economy gain when operating the vehicle. General advantages derived from RVC include improved fuel economy, increased battery life, and increased lamp and switch life.
Vehicle batteries may be used as a power source for externally coupled accessories. For example, a vehicle may tow a trailer, a boat, or other common vehicle accessory for recreation that has a separate auxiliary battery requiring charging. In another example, a road-side assistance truck may assist a stranded vehicle with a drained battery by coupling the truck battery with the drained battery of the vehicle for a “jump start”. Using RVC generally lowers regulated voltage to improve fuel economy but reduces the amount of charging current usually available for charging. Because RVC generally lowers available voltage shortly after starting and idling of a vehicle engine, the drained battery or auxiliary battery may not fully charge in vehicles using RVC.
Accordingly, it is desirable to provide an override for regulated voltage control systems of vehicle battery and alternator operation. In addition, it is desirable to provide an operator-activated override of regulated voltage control systems having a variety of selectable modes of operation. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.